1. Field
Embodiments described herein generally relate to methods for making resin or polymer particles in gel form. More particularly, such embodiments relate to methods for making phenol-formaldehyde resin or polymer particles in gel form that can be further processed into aerogel, xerogel, and/or cryogel particles.
2. Description of the Related Art
Carbon materials such as carbon aerogels, xerogels, and cryogels have been used in a variety of products, such as supercapacitors, to improve their properties. Such carbon materials are typically produced by converting polymer gels into the desired carbon materials. For example, resorcinol and formaldehyde can be used to make precursor solutions (e.g., a “sol,” which is a solution or a colloidal dispersion of particles in a liquid) which can then be processed into large monolithic polymer gels or “sol-gels” by polymerization.
Monolithic polymer gels, however, are difficult and expensive to produce and convert into aerogels, xerogels, or cryogels. Due to the monolith's large size and low thermal conductivity a significant amount of energy, time, and specialized equipment is required to polymerize the monomer components that makes up the monolith structure. Physical differences in the monolithic polymer are also formed which can negatively impact the aerogel, xerogel, or cryogel's performance produced. Such physical differences are often formed due to the uneven heating of the monolithic polymer gel as heat is transferred from the outside to the inside thereof. Furthermore, the large monolithic polymer gel requires physical grinding to reduce its monolithic structure into polymer particles in gel form that can then be processed into the aerogel, xerogel, or cryogel. This additional step is also labor, capital, and time intensive.
There is a need, therefore, for improved methods for making polymer particles in gel form.